This invention relates to a method and apparatus for supplying ingredients to a concrete mixer.
The supplying of concrete at various construction sites is often a problem. The conventional manner for doing this is to provide a plurality of ready mix concrete trucks which have the concrete mixed and which continue to tumble the concrete from the point of mixing to the construction site.
Several problems occur with the ready mix method of conveying concrete to the construction site. One of the most serious problems is a result of the fact that the concrete begins to set up the minute that water is added to it. Thus, if the truck conveying the ready mixed concrete does not empty its contents within a relatively short time, the concrete will set up and harden within the truck. Often times if the construction crew is not ready for the concrete within the truck when it arrives at the site, it is necessary for the driver of the truck to empty the contents rather than to permit them to set up within the truck.
As a result of the tendency of concrete to set up, timing becomes critical with respect to the delivery of the concrete to the construction site. The trucks must be timed to arrive at various time intervals rather than to arrive all at once. The trucks cannot stand and wait for the construction crew to ready the site for the pouring of concrete. The site must be ready at the time the concrete arrives.
The ready mix method of delivering concrete also requires numerous trucks and drivers which increases the cost as a result of the extensive labor and capital which must be invested in the plurality of trucks and drivers.
As an alternative to conveying the ready mixed concrete to the construction site, attempts have been made to mix the concrete at the construction site. This process has the advantage that the ingredients may be carried to the construction site and stored until the concrete is mixed. The water is added only after the concrete is mixed.
However, the mixing of concrete at the construction site also presents certain problems. Cement is a very difficult commodity to handle, particularly with respect to the transporting and conveying of the cement to the cement mixer. The reasons for the difficulty in handling cement arise from its inherent fine powdery consistency and also from its tendency to set up when exposed to moisture or water. When a container of cement is conveyed by a vehicle, the vibration of the vehicle during transit causes the cement to pack down into a very hard consistency. This packing down causes binding of conveyor screws for conveying the cement out of the container into the cement mixer. Often times the conveyor screws are locked as a result of the packing of the cement around them during transit.
Furthermore, the container for carrying the cement must be sealed against moisture and water so that the cement is not exposed to moisture or water with the resulting hardening of the cement.
It is also important that the cement be stored in a container which can be completely emptied in order to make full use of all the cement. The storing of cement in bags on the ground is disadvantageous inasmuch as it results in exposing the cement to moisture which causes setting up of the cement.